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1 // 1 // 2 // ******************************************* 2 // ******************************************************************** 3 // * License and Disclaimer 3 // * License and Disclaimer * 4 // * 4 // * * 5 // * The Geant4 software is copyright of th 5 // * The Geant4 software is copyright of the Copyright Holders of * 6 // * the Geant4 Collaboration. It is provided 6 // * the Geant4 Collaboration. It is provided under the terms and * 7 // * conditions of the Geant4 Software License 7 // * conditions of the Geant4 Software License, included in the file * 8 // * LICENSE and available at http://cern.ch/ 8 // * LICENSE and available at http://cern.ch/geant4/license . These * 9 // * include a list of copyright holders. 9 // * include a list of copyright holders. * 10 // * 10 // * * 11 // * Neither the authors of this software syst 11 // * Neither the authors of this software system, nor their employing * 12 // * institutes,nor the agencies providing fin 12 // * institutes,nor the agencies providing financial support for this * 13 // * work make any representation or warran 13 // * work make any representation or warranty, express or implied, * 14 // * regarding this software system or assum 14 // * regarding this software system or assume any liability for its * 15 // * use. Please see the license in the file 15 // * use. Please see the license in the file LICENSE and URL above * 16 // * for the full disclaimer and the limitatio 16 // * for the full disclaimer and the limitation of liability. * 17 // * 17 // * * 18 // * This code implementation is the result 18 // * This code implementation is the result of the scientific and * 19 // * technical work of the GEANT4 collaboratio 19 // * technical work of the GEANT4 collaboration. * 20 // * By using, copying, modifying or distri 20 // * By using, copying, modifying or distributing the software (or * 21 // * any work based on the software) you ag 21 // * any work based on the software) you agree to acknowledge its * 22 // * use in resulting scientific publicati 22 // * use in resulting scientific publications, and indicate your * 23 // * acceptance of all terms of the Geant4 Sof 23 // * acceptance of all terms of the Geant4 Software license. * 24 // ******************************************* 24 // ******************************************************************** 25 // 25 // 26 // G4MagErrorStepper implementation 26 // G4MagErrorStepper implementation 27 // 27 // 28 // Author: W.Wander <wwc@mit.edu>, 09.12.1997 28 // Author: W.Wander <wwc@mit.edu>, 09.12.1997 29 // ------------------------------------------- 29 // -------------------------------------------------------------------- 30 30 31 #include "G4MagErrorStepper.hh" 31 #include "G4MagErrorStepper.hh" 32 #include "G4LineSection.hh" 32 #include "G4LineSection.hh" 33 33 34 G4MagErrorStepper::~G4MagErrorStepper() 34 G4MagErrorStepper::~G4MagErrorStepper() 35 { 35 { 36 delete [] yMiddle; 36 delete [] yMiddle; 37 delete [] dydxMid; 37 delete [] dydxMid; 38 delete [] yInitial; 38 delete [] yInitial; 39 delete [] yOneStep; 39 delete [] yOneStep; 40 } 40 } 41 41 42 void G4MagErrorStepper::Stepper( const G4doubl 42 void G4MagErrorStepper::Stepper( const G4double yInput[], 43 const G4doubl 43 const G4double dydx[], 44 G4doubl 44 G4double hstep, 45 G4doubl 45 G4double yOutput[], 46 G4doubl 46 G4double yError [] ) 47 { 47 { 48 const G4int nvar = GetNumberOfVariables(); 48 const G4int nvar = GetNumberOfVariables(); 49 const G4int maxvar = GetNumberOfStateVariab 49 const G4int maxvar = GetNumberOfStateVariables(); 50 50 51 // correction for Richardson Extrapolation. 51 // correction for Richardson Extrapolation. 52 // 52 // 53 G4double correction = 1. / ( (1 << Integra 53 G4double correction = 1. / ( (1 << IntegratorOrder()) -1 ); 54 54 55 // Saving yInput because yInput and yOutpu 55 // Saving yInput because yInput and yOutput can be aliases for same array 56 // 56 // 57 for(G4int i=0; i<nvar; ++i) 57 for(G4int i=0; i<nvar; ++i) 58 { 58 { 59 yInitial[i]=yInput[i]; 59 yInitial[i]=yInput[i]; 60 } 60 } 61 yInitial[7] = yInput[7]; // Copy the time i 61 yInitial[7] = yInput[7]; // Copy the time in case...even if not really needed 62 yMiddle[7] = yInput[7]; // Copy the time f 62 yMiddle[7] = yInput[7]; // Copy the time from initial value 63 yOneStep[7] = yInput[7]; // As it contribut 63 yOneStep[7] = yInput[7]; // As it contributes to final value of yOutput ? 64 // yOutput[7] = yInput[7]; // -> dumb step 64 // yOutput[7] = yInput[7]; // -> dumb stepper does it too for RK4 65 65 66 for(G4int i=nvar; i<maxvar; ++i) 66 for(G4int i=nvar; i<maxvar; ++i) 67 { 67 { 68 yOutput[i]=yInput[i]; 68 yOutput[i]=yInput[i]; 69 } 69 } 70 // yError[7] = 0.0; 70 // yError[7] = 0.0; 71 71 72 G4double halfStep = hstep * 0.5; 72 G4double halfStep = hstep * 0.5; 73 73 74 // Do two half steps 74 // Do two half steps 75 // 75 // 76 DumbStepper (yInitial, dydx, halfStep, 76 DumbStepper (yInitial, dydx, halfStep, yMiddle); 77 RightHandSide(yMiddle, dydxMid); 77 RightHandSide(yMiddle, dydxMid); 78 DumbStepper (yMiddle, dydxMid, halfStep, y 78 DumbStepper (yMiddle, dydxMid, halfStep, yOutput); 79 79 80 // Store midpoint, chord calculation 80 // Store midpoint, chord calculation 81 // 81 // 82 fMidPoint = G4ThreeVector( yMiddle[0], yMi 82 fMidPoint = G4ThreeVector( yMiddle[0], yMiddle[1], yMiddle[2]); 83 83 84 // Do a full Step 84 // Do a full Step 85 // 85 // 86 DumbStepper(yInitial, dydx, hstep, yOneStep 86 DumbStepper(yInitial, dydx, hstep, yOneStep); 87 for(G4int i=0; i<nvar; ++i) 87 for(G4int i=0; i<nvar; ++i) 88 { 88 { 89 yError [i] = yOutput[i] - yOneStep[i] ; 89 yError [i] = yOutput[i] - yOneStep[i] ; 90 yOutput[i] += yError[i]*correction ; 90 yOutput[i] += yError[i]*correction ; 91 // Provides accuracy increased by 1 or 91 // Provides accuracy increased by 1 order via Richardson Extrapolation 92 } 92 } 93 93 94 fInitialPoint = G4ThreeVector( yInitial[0], 94 fInitialPoint = G4ThreeVector( yInitial[0], yInitial[1], yInitial[2]); 95 fFinalPoint = G4ThreeVector( yOutput[0], 95 fFinalPoint = G4ThreeVector( yOutput[0], yOutput[1], yOutput[2]); 96 96 97 return; 97 return; 98 } 98 } 99 99 100 G4double G4MagErrorStepper::DistChord() const 100 G4double G4MagErrorStepper::DistChord() const 101 { 101 { 102 // Estimate the maximum distance from the cu 102 // Estimate the maximum distance from the curve to the chord 103 // 103 // 104 // We estimate this using the distance of th 104 // We estimate this using the distance of the midpoint to 105 // chord (the line between 105 // chord (the line between 106 // 106 // 107 // Method below is good only for angle devia 107 // Method below is good only for angle deviations < 2 pi, 108 // This restriction should not a problem for 108 // This restriction should not a problem for the Runge cutta methods, 109 // which generally cannot integrate accurate 109 // which generally cannot integrate accurately for large angle deviations. 110 110 111 G4double distLine, distChord; 111 G4double distLine, distChord; 112 112 113 if (fInitialPoint != fFinalPoint) 113 if (fInitialPoint != fFinalPoint) 114 { 114 { 115 distLine = G4LineSection::Distline(fMidPo 115 distLine = G4LineSection::Distline(fMidPoint, fInitialPoint, fFinalPoint); 116 // This is a class method that gives di 116 // This is a class method that gives distance of Mid 117 // from the Chord between the Initial a 117 // from the Chord between the Initial and Final points. 118 118 119 distChord = distLine; 119 distChord = distLine; 120 } 120 } 121 else 121 else 122 { 122 { 123 distChord = (fMidPoint-fInitialPoint).mag 123 distChord = (fMidPoint-fInitialPoint).mag(); 124 } 124 } 125 125 126 return distChord; 126 return distChord; 127 } 127 } 128 128